1. Field of the Invention
This invention relates generally to weighing apparatus and particularly to portable, low profile weighing scales. The weighing scale provided by this invention is useful for weighing and balancing aircraft and land vehicles efficiently, reliably and accurately.
2. Background Information
Applicants Kroll et al. disclosed scales in U.S. Pat. Nos. 4,714,121, 4,979,581, 5,232,064, and 5,646,376, and load cells in U.S. Pat. Nos. 4,775,018, 4,813,504, and 5,228,527. The scales and load cells handle a broad range of weights and have varying degrees of accuracy. Additionally, the scales have varied designs in terms of height, weight, portability and method of use. A common design factor shared by all of these scales and load cells is that in each, the mounting of the load cell in and to the scale is unique and provides a significant advantage over the prior art.
Wheel scales or platform scales are commonly used to measure axle weight loads of vehicles and aircraft. While some scale devices are designed to accommodate the multiple wheels of dual tandem rear axle assemblies of commercial trucks, most wheel scale devices have a single platform to measure the load from single or dual wheels. The weighing scale assemblies and load cell structures of the present invention are particularly useful for weighing and balancing a variety of sizes and types of private, commercial and military aircraft, and for weighing a variety of sizes and types of land vehicles. These scales can be used either alone or in combination with other scales. To weigh a land vehicle for example, a pair of wheel scales is spaced apart and the vehicle is driven onto the scale platforms one axle at a time for all axles. Each axle weight load is recorded and the summation of axle weights yields the gross weight of the vehicle.
Wheel scales utilizing load cells for weighing axle loads of motor vehicles are known in the weighing art. Additionally, wheel scales which utilize strain gauge sensors fixed to deflectable load cells are known. However, the specific configuration of the load cells utilized in prior art scales, the placement of the load cells in these scales, and the cooperation of the active and inactive elements of these prior art wheel scale devices often yield complex and bulky wheel scales which are inaccurate and unrepeatable under many conditions of use.
Prior art wheel scale devices have been proposed and manufactured to use various types of load cell configurations for the purpose of yielding a lightweight, low profile and accurate portable wheel scale. Additionally, various wheel scale structures have been proposed and manufactured wherein these load cell configurations have been utilized with varying cooperative elements. However, these prior art wheel scale structures have often been difficult to use and transport, have been susceptible to damage, and have required the precise placement of loads to achieve reasonable scale accuracy and repeatability.
It is an object of this invention to provide a weighing scale that may be used to weigh and balance aircraft, as well as other vehicles. A further object of this invention is to provide electronic, strong, lightweight, low profile scales which are economical, easily manufactured and which yields reliable and repeatable weighing results with a high degree of accuracy. It is a particular object of this invention to provide a scale that has an improved platform member, an improved structure for mounting one or more load cells to a base member, and an improved engagement structure for effectively transferring a load force from the platform member to the load cells.